Multiple boiler control system



Feb. 5, 1957 .1. E. LA RocQUE ETAL 2,780,205

MULTIPLE BOILER CONTROL SYSTEM 4 Sheets-Shea?l 1 Filed June 25, 1953 3Q@ mamme s@ w @modi Feb. 5, 1957 J. E. A RocQuE E1- AL 2,730,206

MULTIPLE BOILER CONTROL SYSTEM Filed June 23, 1953 4 Sheets-SheelI 2 n/w PRESS ED CAM CONT/:C715

MINUTES Feb. 5, 1957 J, E. LA RocQuE :TAL

MULTIPLE BOILER CONTROL SYSTEM Filed June 23, 1953 4 Sheets-Sheet 5 CVRCU/T IVO-2 Feb. 5, 1957 J. E. LA ROCQUE ETAT. 2,780,206

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United States Patent MULTIPLE BolLER CONTROL SYSTEM Joseph E. La Rocque, Chicago, and Charles E. Impey, Lombard, Ill., assignors to Vapor Heating Corporation, Chicago, Ill., a corporation of Delaware Application June 23, 1953, Serial No. 363,548

9 Claims. (Cl. 122-448) The present invention relates to an improved control system for automatically regulating the operation of a multiple boiler steam generating plant to meet a varying demand for steam.

Steam generating plants of the type herein shown may be used advantageously and economically in situations in which the demand for steam fluctuates to a considerable extent from time to time. For example, the heating of railway passenger cars which are temporarily out of service and stationed in railway terminal yards. When such terminal yard is lled with trains of passenger cars the demand for steam may be very high and require the full output capacity of several steam generators. At other times, with only one or two trains of cars on hand, the demand may be considerably reduced and require the output of but a single generator. Likewise in large laundry establishments when the plant is in full capacity operation, the services of several steam generators may be required while at other times, during night operation for instance, a single generator or two at the most may be adequate to care for the demand for steam.

These are but two suggested situations in which multiple steam generating units may be used and to which the present control mechanism may be advantageously applied. However other uses for such a system will readilysuggest themselves. Regardless of the particular use to which the multiple boiler system may i be put, the control system of this invention is designed to automatically regulate the operation of the system to satisfy varying demands for steam at any time without needlessly exceeding the demand and without requiring a large maintenance personnel to manually regulate the operation of the generators.

According to the invention a control system is provided whereby when the demand for steam, as reected by the steam pressure maintained in a header or manifold connected to a series of generators, is sufliciently low that a single generator is capable of satisfying the demand; one generator of the series is set into operation to satisfy that demand. If the first generator fails to supply the necessary volume of steam within a predetermined time period its output is augmented by the automatic setting into operation of a second generator calculated to deliver the necessary additional steam to provide the desired pressure in the common header. Similarly, if the first two generators do not supply the amount of steam required to maintain the desired steam pressure, a third generator will be set into operation and thereafter, if the demand is not satised, additional generators will be brought into operation in succession until such time as all of the available generators are operating. However, if after a particular generator has been set into operation the desired steam pressure is attained in the said header, no further generators will be set into operation. The generators which have been put into operation will be maintained in operation until such time as the demand for steam warrants Ydisabling of fit) ICC

one or more of them. In such an instance the present control system is designed to automatically cut out of operation one or more generators until the steam pressure in the header is reduced a point. In order to accomplish this result, the system operates to disable the generators in the reverse order from which they were initially brought into operation.

In bringing the various generators into operation or in cutting them out of operation, the fire and water are controlled automatically to protect the generator structure. For example, prior to cutting a particular generator into operation certain routine procedure wherein the fuel and atomizing air apparatus are rst set into operation, followed by operation of the water pump and blower apparatus is invariably followed. Similarly in shutting down a generator from -a full tire condition to a stand-by condition the fuel and air apparatus is iirst disabled and the water pump is allowed to run for la short period of time so as to cool the generator and insure the fact that the coils are filled with water and that the generator is leftin a stand-by condition prior to a subsequent operation.

The control apparatus as briefly outlined above will so function that the operation of a generator may be interrupted after the generator has been selected for operation and before it has reached its full operation, if the demand for steam is such as to indicate that the service of the generator is not required. In this connection, the portion of the control apparatus which affects the operation of the selected or partially operated generator will complete a cycle which may not necessarily bring the generator to full operation but which nevertheless will leave the generator in readiness for a subsequent operation if a later demand for steam requires its operation. M

Other objects and advantages of the invention, not at this time enumerated, will be expressed as a further statement of invention after a description of one particular steam generating plant to which the invention is applicable has been made and after its intended operation has been set forth. In this manner a better understanding of the principles of the invention may be had and repetitions description of function will be avoided.

In the accompanying drawings, one illustrative embodiment of the invention has been shown, wherein:

Fig. l is a schematic view of a multiple boiler steam generating system or plant provided with the improved control system of the present invention;

Fig. 2 is a View partly in section and partly in elevation illustrating a steam generator unit and showing the several electrical control elements associated therewith;

Fig. 3 is a circuit diagram showing the said electrical control elements connected in their associated control circuits;

Fig. 4 is a schematic view of an electrically operated timing control mechanism employed to initiate and control the opei'ation of the control apparatus of the individual steam generators of the system;

Fig. 5 is a timing chart illustrating the operation of the timing control mechanism of Fig. 4.

Multiple llm't steam gen-@rating system Referring to the drawings and in particular to Fig. l, a multiple-unit steam generating system is designated generally by the reference numeral i0 and includes a plurality of substantially identical steam generators. For convenience of illustration, a bank of seven such units `are shown schematically and the individual generators are designated 10a to 10g inclusive. It will be understood, however, that a greater or lesser number of such units may be employed according to the desired maximum capacity of the system. The steam generators are prefer ably, though not necessarily, of the watentube type. For convenience, the Ysteam generator' 10al is'shown vin Fig. 2. Water is drawn from a source of 'supply 11 by means of the individual feed vpump 12 associated with leach of the steam generators. The flow path of the water includes a manifold supply line 13 and a series of branch pipes 14 in which the feed pumps 12 are interposed to deliver the water to a eoil 15 (see Fig. 2) of its associated generator 10o-19g as operating conditions may require. Hot water and steam discharged from any one of the steam generators is received by an associated steam separator 15. The steam passes from the top of the separator through a pipe 17 and check valve 18 into a steam header 19. The water separated from the steam is discharged from the separator 16 through a branch conduit ,20 into a water' return manifold 21 leading back to the source 11.

Fuel, which preferably is oil, is supplied from a fuel tank 22, to a Asprayl head or nozzle 23 of each steam generator Y througha fuel'supply manifold 24 and branch conduit 2 5 in which there is interposed a fuel pump 26 and a solenoid opened fuel valve 27, 'which is energized open'. Compressed air'fo'r atomizing the liquid fuel is delivered to the spray head 23 4through a branch conduit 28"leading from ariV air supply manifold 29. Each air branchY VAconduit isV provided with a solenoid opened valve 30. Y

The water pump 12 is operated by a motor 31 and the combustion air is supplied to the fire chamber by means of a blower 32. The fuel pump 26 is preferably operatively connected with the operating shaft of the blower 32 and the blower is operatively connected, for example by means of a belt 33 with the motor 31, whereby the fuel pump, blower and water feed pump :are all operated by the motor 31. Consequently, when it is desired to shutoff the delivery of fuel while the blower 32 and the pump 12 continue theirA operation, a fuel by-pass valve 34' opened either electrically or by pressure permits the fuel in branch pipe 25 to return to the fuel tank 22 through branch pipe 35 and manifold return pipe 36.

The steam header 19 may be employed for supplying steam to all manner of steam powered equipment such as heat exchangers, turbines, steam engines, nozzles, steam expansion or steam escapement devices and the like. Such devices have not been illustrated herein but it will be understood 'that each device is operatively connected to the header 19 by a suitable steam take-off or leader line such as the lines indicated at 37.

Individual generator Control The control of the multiple steam generators 10a-10g involves the exercise of control, by means of master and individual timers (Fig. 4) of the individual control systems of the several generators. It is deemed desirable, therefore, to describe the operation of the individual control system for one of the generators before describing the manner in which the individual generators are cut in and out of the multiple control system.

Referring now to Figs. 2 and 3.: Certain. of the control elements are illustrated( in Fig. 2, and these elements, together with other elements not shown in Fig. 2, are connected in the circuit diagram shown in Fig. 3. The component parts of the control mechanism of Fig. 3 includes a manual cut-out switch X interposed in positive line P, a main switch A capable of being set for either manual control or for automatic control under the influence of the timing mechanism of Fig. 4. The main switch A may be a rotary type switch having contacts 1 to 6 inclusive adapted to be opened fand closed in predetermined sequence, but the particular construction of the switch is not important for an understanding of the present invention. Therefore, it can be regarded as six manually operated contacts 1 to 6 inclusive.

The system further includes four relay operating switches including a master relay B having movable contacts 1, 2 and 3; a motor control relay C having contacts 1 to 4 inclusive; a single Contact alarm relay D; a single contact interlock rclay E; a single contact out-fire relay F; a temperature control switch G having contacts 1 and 2; a relay control switch H which operates under the control of a photo-electric cell (I) disposed in the fire chamber of the generator and having a manual cut-out switch J; and a water pressure switch K having contacts 1 and 2 controlled by the water pressure, the contacts being operable under the control of a pressure actuated element L whereby contact 1 is opened during the presence of water pressure and contact 2 is closed during the presence of water pressure in the generator.

Additional operating devices associated with the system are relay actuating magnets B', C', D', E and F for the relays B, C, D, E and F, respectively.

The various operating elements illustrated in Fig. 3 are shown in the positions which they assume when the manual switch X is closed, but the main switch A is in its off position. In this position the contact 2 of said main switch is closed. The closing of the manual Vswitch X establishes circuit No. 1 for energizing motor generator M which in turn energizes a transformer Q for supplying electrical current to a spam plug 38 (Fig. 2). Also, a visual signal, for example an electric light 0" is interposed in a circuit No. 2 connected across the positive and negative lines of the system.

When the main switch A is in its off position its No. 2 Contact is closed, thereby establishing circuit No. 3 for energizing the master relay B. This circuit leads from the positive line P through lsaid No. 2 contact of the main switch A, leads 39, 4b, relay magnet B and lead 41 to the negative line N. The energization of relay B closes its No. 1 and 2 contacts and opens the No. 3 contact. A circuit No. 4 leads from positive line P through lead 42 through a normally closed contact 1 of relay E, leads 43 and 44 through the magnet F of out-firc relay F and thence through lead S5 to the negative line N. A second circuit designated No. 5 is also effective for energizing the out-fire relay. This circuit leads from positive line P through lead 46, normally closed contact 2 of relay C, leads 47 and 44 through the magnet F and lead 45 to the negative line N.

Assuming that there is no water pressure in the generator, the contact No. 1 of water pressure switch K is closed and thereby establishes a circuit No. 6 through the magnet F of said out-fire relay F. This circuit leads from positive line through lead 4S, contact No. 1 of water pressure switch K, leads 49 and 44, magnet F and lead 45 to the negative line N. The energization of the out-fire relay F by any one of the said circuits 4, 5 or 6, establishes a holding circuit for maintaining the master relay B energized. This holding circuit is designated circuit No. 7 and leads from the positive line P through a normally closed `low temperature No. 1 contact of temperature switch G, lead Sil, energized closed No. 2 contact of master relay B, lead 51 through energized closed contact of out-fire relay F, leads 52 and 53 and leads 54 and 40, magnet B of relay B and thence through lead 41 to the negative `line -N. This holding circuit (circuit No. 7) will be effective to maintain the master relay B energized so long as the out-fire relay F is energized closed. The said out-fire relay F is cons-tructed to delay its opening for five seconds after all energizing circuits therefor have been opened. This feature is not important for the present, but is important as a safety measure to interrupt the operation of the system in the event of failure of fuel to ignite for a period of five seconds. Y

The heating coil 15 of the generator is filled with water before fuel is ignited in the fire chamber of the generator. The operation for filling the coil is accomplished by positioning main`V switch A to open its No. 2 contact and close its N o. 5 contact. This operation of thc main switch can be effected, without disturbing the closed position of the master relay B, since its holding circuits through the out-fire relay (circuits Nos. 4, 5 and 6) remain effective.

avdeoe The closing of `said No. 5 contact of the main switch A establishes an energizing circuit for the relay C and thereby effects energization of the motor 31 for operating the fuel pump 1-2. The circuit for energizing relay C is designated circuit No. 8 and extends from the positive line P through the closed contact 5 of the main switch A, lead 5S, energized closed contact 1 of relay B, lead 56, magnet C', of relay C and thence through lead 57 to the negative line N. The energization of relay C opens its contact No. 2 and, therefore, breaks circuit No. 5, but closes its contact Nos. 3 and 4 to establish an operating circuit designated circuit No. 9 through the motor. This circuit extends from positive line P through lead 58, energized closed contact 3 of relay C, lead 59 through the motor 31 and thence through negative lead 60, energized closed contact 4 of relay C and lead 61 to the negative line N.

The said motor 31, in addition to operating the said pump 12, also operates the fuel pump 26 and the blower fan 32, but the fuel valve 27 is de-energized during the coil filling operation, and, consequently, the fuel from pum-p 26 is by-passed through the by-pass valve 34% and conduit tothe yfuel tank, the by-pass valve 34 being opened in this instance by pressure of the fuel created by the operation of pump' 26 while the fuel valve 27 is closed. 1f it is desired to continue the operation of the generator under manual control, the contact No. 5 of the main switch remains closed and the contact No. 4 is closed andthe operation just described is continued until the water pressure in the generator coils 15 is sufficient to close No. 2 contact of pressure switch K and opens No. 1 contact thereof. The closing of the said No. 2 contact of pressure switch K establishes circuit No. l0 for energizing open the fuel valve 27 and the air valve 30 to deliver atomized fuel into the rire chamber of the generator where it is ignited by the sparking plug 38 of the ignition circuit. The said circuit No. 1G leads from positive line P through the closed contact 4 of the main switch A, lead 62, energized closed contact No. 1 of relay C, lead 63, closed contact No. 2 of pressure switch K and lead 64 through the magnet winding 65 of fuel valve 27 and lead 66 to the negative line N. The air valve 30 is connected in parallel with the fuel valve 27 by means of a branch lead 67 connected in lead 64 and extending through magnet winding 68 and lead 69 to the negative line N. The closing of contact No. 4 of the main switch A establishes a second circuit designated 16a for energizing the interlock relay E and thereby de-energizing circuit No. 4 through the magnet lli of relay F. The circuit lita leads from a junction in lead 62 through leads 7l), 7l, magnet E of relay E and lead 72 to the negative line N. It will be noted in this connection that circuit No. 6 for energizing the magnet :F of out-tire relay F is also deenergized by the opening of the low pressure contact No. 1 of pressure switch K. Consequently, all energizing circuits through the magnet F of out-rire relay F are now de-energized. However, the relay F is constructed to remain closed for a period of ve seconds after its energiz ing rcircuits have been open. lf the fuel fails to ignite in the lire chamber within the period of ive seconds the relay F is tie-energized to open its contact and thereby opens the holding circuit No. 7 through the magnet B' of the master relay B and thereby de-energizes the control system. However, the ignition of the fuel in the tire chamber within said period of five seconds results in activating the photo-electric cell (l) so as to close relay contact H and thereby establish a holding circuit through the magnet B of master relay B, which holding circuit maintains the master-relay energized as vlong as ignition of the fuel continues in the generator, This circuit is desig nated circuit No. la and extends from a connection in lead 51 through lead 73, closed contact 74 of relay H, lead 75, closed manual cut-out switch J, leads 76, 54 and 40 through the relay magnet B' and thence through lead 41 to the negative line N.

6 yThe manual operation may be interrupted by opening the No. 4 and No. 5 contacts of the main switch and closing switch No. 2 whereupon the delivery of fuel and feed water to the generator is discontinued and the control elements of the system are returned to the positions illus- Steam generator automatic control After the generator has been iiilled with water and is otherwise conditioned for operation, the main switch A is set for automatic operation. In this position of the switch A its contacts Nos. 1 and 6 are closed and its contacts 2, 3, 4 and 5 are open. The control elements B, C, D, E, F, will assume the positions shown in Fig. 3 by virtue of the existence of circuit No. 7. The valves 27 and 39 will 'be closed and the low temperature contact No. 1 of temperature switch G will be closed. Closure of the Nos. 1 and 6 contacts of said main switch A are ineeetive at this time inasmuch as they are in series, respectively, with timer cam contacts 77 and 78, which are open. However, the generator otherwise stands in readiness for operation when called for by closure of the cam operated timer contacts 77 and 78.

At this point it should be noted that the entire control apparatus attains a static condition with certain circuits under energization and certain other circuits potentially available for energization, all awaiting closure of the timer controlled contacts 77 and 78to place the generator in immediate operation. The opening and closing operations of the contacts 77 and 78 under the control of the timer mechanism of Fig. 3 will be described subsequentlybut for the present the function of these contacts 77 and 78 in the system will be set forth.

Closure of the timer Contact 77 establishes a circuit through magnet E and thereby energizes relay E to open circuit No. 4 through the out-tire relay magnet F. The closing of timer contact 78 re-establishes parts of circuits No. 8 so as to energize relay C and thereby open circuit No. 5 through out-fire relay magnet F and closes the circuit No. 9 through the motor 31 to initiate operation of the pump 12. Operation of the pump 12 produces sucient pressure in the water coil 15 to open closed contact No. 1 of pressure switch K and thereby open the remaining energizing circuit (circuit No. 6) through magnet F of out-fire relay F. However, as before indicated, the out-fire relay remains closed for tive seconds after its energizing circuits are opened. The water pressure in the generator coil 15 also closes the contact No. 2 of pressure switch K and thereby completes parts of circuits Nos. 10 and 10a to energize open the fuel valve 27 and the air valve 30. The parts of circuits 10, 10a thus established lead from the positive line P through closed contact No. 1 of main switch A, closed timer contact 77, leads 71, 70, 62, closed contact No. 1 of relay C, lead 63, closed contact 2 of pressure switch K, magnet coil of fuel valve 27 and lead 66 to negative line N. The air valve 30 is simultaneously energized open by a branch lead 67 extending through magnet coil 68 of valve 30 and thence through lead 69 to the negative line.

Ignition of the fuel delivered into the fire chamber will normally take place within the period of five seconds that the out-lire relay remains closed. Such ignition activates the photo-electric cell I and thereby closes the contact 74 of relay H and thereby establishes a holding circuit 7-7a and part of circuit No. 3 to maintain the master relay B energized, so long as the ignition continues in the re chamber.

If for any reason the temperature at the discharge end 17 of the generator exceeds a predetermined maximum, a thermal element 79 of the temperature switch G functions to close its No. 2 contact. The closing of No. 2 temperature contact energizes the solenoid of the fuel bypass valve 34 and thereby cuts off two-thirds of the normal volume of fuel delivered to the fire chamber. This redown the boiler operation.

duction in the delivery of fuel is accomplished without atecti'ngthe delivery of water. The circuit for `energizing open the fuel by-pass valve 34 extends from positive line iP through closed contact No. 2 of temperature switch vGand lead 83 through the solenoid of by-pass valve 34 and thence to negative line N.

If the reduction of the fuel delivery is sufficient to correct the high temperature conditions of the steam and thereby prevent the development of superheated steam, the Contact No. 2 will again open and the full operation of the generator will be resumed. However, il' the steam temperature at the outlet 17 increases above such maximum, contact No. 1 of temperature switch G will open and thereby open the hording circuit 7 and 7a through the 'solenoid E of relay B. The opening of the said holding circuit and consequent de-energization of relays B and C opens the operating circuits Nos. 9 and 10a so as to shut The de-energization of relay B also closes its contact No. 3 and thereby energizes the signal R to notify the attendant that the boiler requires inspection. After the boiler is completely shut down, it cannot be again activated until certain manual adjustments are made as follows:

( l). The temperature switch G must be manually reset -to close its Contact No. 1 and open its contact No. .2.

(2). The main switch A must be turned to its olf position so as to close its contact No. 2 and thereby establish lan energizing circuit through solenoid B' to close contacts No. 1 and No. 2 of relay B.

(3). lf the water coil 15 is lled with water the No. 2 Contact of water pressure switch K will be closed and if the timer switch 7S still remains closed the boiler may be set into operation by shifting main switch A from its off position to its automatic run position to close its switch contacts Nos. 1 and 6. However, if the water coil 15 is 'not filled with water the No. 2 contact of pressure switch K will be open. Consequently, the main switch must be turned to a position to fill the water coils as previously described and thereby open the No. 1 contact of pressure switch K and close its No. 2 contact before fuel will be delivered into the fire chamber of the boiler.

Multiple generator' control lt will be seen that the demand for steam by the various steam-consuming devices connected to the several conduits 37`will vary widely, depending upon the number of such devices actually in operation at any given instant and according to the combined steam consuming capacity of the devices in operation at such time. This demand for steam will, of course, be reflected by the varying pressure of steam existing within the header 19.

According to the present invention, control means are provided whereby when the demand for steam is sufriciently low that a single generator is capable of satisfying this demand, the generator' 10a will be set into operation to supply the necessary head or steam. if the continued demand does not exceed the capacity of the single generator, that generator i Iill remain in operation indefinitely to maintain the necessary balance of steam pressure in the header i9. lf, however, the single generator lila fails to maintain the 'desired steam pressure in the header i9, a second generator' Mib is set into operation to augment the supply of steam delivered to the header. lf and when the demand for steam increases beyond the'capacity of the said two generators, additional generators are cut in until such time as all of the available generators 10a-10g in the bank are in operation.

The control system is so designed that-when -two or more generators 10a, tb, etc., are in operation and` the 'demand for steam is decreased andas a result of the reduced demand, the steam pressure within the header 19 rises above a predetermined maximum, one of the general8 mand for steam is further decreased to such an extent as to justify theshutting down of one or more additional generators, these additional generators will be automatically cut out successively at predetermined time intervals.

According to the present control System, the various generators 10a to 10g inclusive are cut into operation in a definite sequential order, i. e. in the order named as the demand for steam increases. Likewise during a decrease in the demand for steam the various generators are cut out of operation in the reverse order so that in such an instance the last generator which has been set into operation will be the first generator to be cut out of operation. Furthermore, the control system is so designed that in the event that after a particular generator has been set into operation due to a sudden increased demand for steam, if that demand is reduced before the the generator attains its full operation, the firing-of the generator is interrupted, but its feed water pump will continue operations to cool vdown the generator and insure the fillingof the water coils thereof so as to leave the generator in readiness for a subsequent operation if occasion so demands.

The multiple generator control system of the present invention is predicated upon the use of the individual control mechanism hereinbefore described for generators 10a to 10g inclusive, together with a timing mechanism such as shown schematically in Fig. 4, which timing mechanism is employed for the purpose of controlling the operation of the various individual control apparatus. The timing mechanism of Fig. 4 is cyclic in its nature and is capable of a complete cycle of operation from an initial starting time until completion of a full cycle, during which time it will cause all of the generators 16a to 19g to be sequentially cut into operation at definite spaced time intervals. The mechanism is also capable of being interrupted or reversed'in its cyclic operation as the demand for steam in the header 19 lags or falls.

The cycling operations of the timing mechanism of Pig. 4 is responsive to and depends solely for its reversible operations on a rise or fall of steam pressure from a predetermined normal in the steam header 19 as evidenced by the pressure exerted upon the respective diaphragms 85--86 of a pair of pressure actuated switches 87-88 (Fig. 1) operatively connected to the header 19. Said timing mechanism comprises a reversible master timer S and a number of sub-timing units T-1 to T-7, including a unidirectional motor Ma to Mg, respectively, are associated with the several generators. The master timer includes a plurality 0f time operating cams S1', S-1 to S-7, inclusive, and Sf each of which, except Sr and Sf, when once set into operation, will activate a non-reversible sub-timer' to set its associated steam generator 10a-10g into full operation. Each of these sub-timing units T-l to T7, inclusive, is operatively associated with one of the individual generator control systems shown in Fig. 3; the latter, when set up for automatic operation, is responsive to its ovm sub-timer T-l to T-7, respectively, for cutting into or out of operation. All of the sub-timing units T-1-T-7 are responsive to the reversible master control S in a definite sequential order or pattern and the master control S operates on a predetermined time basis so that during an uninterrupted operating phase of the master timer for increasing the number of operating generators, the sub-timing units T-l to T-7 will initiate their individual cycles at equally spaced intervals of time. Each subtiming unit T-l to T-7, once it has entered upon its unidirectional cycle of operation, will progress to a midcycle point wherein it causes the control mechanism (Fig. 3) of its associated generator to bring the generator up to full operation and at that point the sub-timer unit will automatically come to rest. If the operation of the master timer continues in a direction to increase the number of operating generators, the activated subunits will remain inactive with their associated generators in full operation untilsuch time as the cam Sf of the master timer S is operated to open the forward circuit through the timer motor Uf and the cam Sr operates t close a circuit through the reversing timer motor Ur. On a reverse operation of the master timer cams S-1-S-7, the sub-timing units are successively released from their mid-cycle point and are allowed to finish out their previously commenced cycles. During the reversal of operation of the master timer S the sub-timer units exert an influence on the generator control mechanism to cut out the generators successively, while at the same time maintaining the cut-out generators in condition for subsequent instant operation if occasion demands.

T mer control mechanism As previously set forth, the timer control mechanism of Fig. 4 is designed to control the operation of all of the steam generators a to 10g inclusive, cutting them in one at a time and successively as the demand for steam in the header 19 rises and cutting them out singly and in the reverse order as the demand for steam diminishes. The timer mechanism operates under the control of the said pressure switches 87 and 88.

In certain installations the demand for steam during one period of time may be greater than the demand for steam during a diierent period of time. Such class of operation may be prevalent in the operation of large laundry and dry cleaning establishments, particularly where a night shift is not employed and where, as a consequence, machinery operation is relatively heavy during the day and relatively light or non-existent at night. Similarly, in bus or railroad terminals where according to schedule a large number of vehicles may be on the stand-by line during certain hours and only a few at other hours, this class operation is required. Purely for purposes of illustration herein, it is assumed that the class of operation illustrated is applicable to day and night maintenance where operating steam pressures are to be maintainedV in a range of from approximately 105 pounds to approximately 115 pounds during the day and in very low range not exceeding 90 pounds at night. Obviously these ranges may be varied if desired and a greater number of ranges may be accommodated by the simple expedient of providing additional pressure responsive circuitry.

Referring now to Fig. 4 in detail, the previously men- .tioned pressure operated switch 87 is responsive to relatively loW steam pressure in the header 19. Accordingly its No. 1 contacts are designed to close at l pound of pressure and to open at 2 pounds. Its No. 2 contacts are adapted to close at 90 pounds and to open at 89 pounds. The switch 88 is responsive to higher pressures and its No. 1 contacts close at 104 pounds and open at 105 pounds. Its No. 2 contacts close at 115 pounds and open at 114 pounds. It will be understood rthat the pressures specied are purely arbitrary and in practice they may be approximate pressures.

A selector switch V is provided with contacts 89 and 90 and Vis arranged in series relation to each of the switches 87 and 88 and to a circuit breaker switch W.

With the switch W closed and with the switch V set for day operation with its contact 90 closed, a circuit will exist from the positive line Y through the contact 90 of the switch V, leads 100, 101, No. 1 contacts of the switch 88, leads 102, 103, cam controlled contacts 104, lead 10S, motor Uf and lead 106 to the negative line Z.

The motor Uf is a unidirectional motor and it is operatively connected to a cam shaft 107 on which there are mounted a series of seven cams S-1 to S-7 inclusive, one for each of the steam generators 10a to 10g inclusive, and two additional cams including a forward drive cam Si and a reverse drive cani Sr. The cam Sr controls the opening and closing movements of a pair of contacts 10S disposed in the circuit ot a motor Ur. The'motor Uf, when energized serves to drive the cam shaft 107 in a forward direction as indicated by the arrow while the motor Ur when energized serves to drive the shaft 107 in a reverse direction, likewise indicated by the arrow.

Each of the cams S-l to S-7 inclusive constitutes a master control cam for initiating operation of one of the previously mentioned sub-cycle units associated with the timing mechanism. The sub-cycle Vunits are designated' as T-1 to T-7 inclusive and each controls the operation or" one of the steam generator units 10a to 10g inclusive as far as its cutting-in and cutting-out operations are concerned. rl`he various sub-cycle units T1 to T-7 inclusive are identical in their mechanism construction aswell as in their electrical function with respect to the particular control mechanism of Fig. 3 which they in turn control. Therefore, a description of one of these sub-cycle units will sufce for all such units. The unit '1"-1 has been selected for descriptive purposes and similar reference characters have been applied to certain of the other units.

As soon as the pressure of steam in the header 19 attains its setting of 104 pounds, the No. 1 contacts of the switch 88 will close to establish the previously described circuit through the motor Uf and initiate forward rotational movement of the cam shaft 107. Immediately thereafter the contact 108 of cam Sr will close without functionvbecause the No. 2 contacts of the switch 88 are open. The No. 2 contact of the cam S-l of master timer (normally closed at this time) is adapted to remain closed for a period of one minute after closure of the main circuit switch W due to a dwell 109 provided in the cam. When this period of time has elapsed the No, 2 contact of the cam S-1 becomes open and the No. 1 contact closes, thereby energizing a unidirectional timing motor Mn through a circuit leading from the line Y through lead 110, motor Ma, No. 2 contact of a timer cam Ct-l, lead 111, No. 1 contact of the cam S-1 to the negative line Z.

The timer cam Cl-l, together with three other timer cams Ct-2, 4Ct-3 and Ct-4 are disposed on a motor shaft 112 for movement in unison. The shaft 112 is adapted to make one complete revolution in six minutes unless previously interrupted. The cam Ct-l is provided with a one minute dwell 113 during which dwell the No. 2 contact of its switch remains closed with the No. 1 contact open. The cam Ct-3 has a one minute dwell 115 for maintaining its switch 77 (see individual boiler control Fig. 3) closed. The cam Ct-4 has a tive minute dwell 116 for maintaining its switch 78 closed.

As shown in the timing chart of Fig. 5 the dwell 113 is effective immediately upon energization of the timer motor Mn; the dwell 114 is effective fifteen seconds after the motor Mn is energized; the dwell 115 is effective thirty seconds after the motor is energized, and the dwell 116 is effective forty-five seconds after the motor is energized.

With the N0. 1 contacts of the control cam S-l closed and the motor Ma in operation, the No. 2 contact ot the cam Ct-Z will close at fifteen seconds in the cycle (see chart-Fig. 5) and establish a concurrent parallel circuit with the previously described motor circuit which extends through lead 110, motor Ma, No. 2 contact of the cani Ct-l (still closed), lead 120, No. 2 contact of the cam Ct2, and lead 121. At thirty seconds in the cycle, the switch 77 of the cam Ct-3 closes. This function results in energizing relay E and thereby opens circuit No. 4 through out-tire relay magnet F. The closing of said switch 77 also conditions circuits 10 and 10a so that they will be effective to energize open the vfuel and air valves 27, 30 whenNo. 1 contact of relay C is closed and No.V 2 contact of pressure switch K closes. At 45 seconds the switch 7S of the cam Cr-4 closes to energize circuit No. 8 and thereby energize relay C to open its contact No. 2 so as to break out-tire magnet circuit No. 5

and also close contacts I, in fuel and air valve circuits 10, 10a' and to close contacts 3, 4 and 5 of said relay to complete said motor operating circuits Nos. 9 and 9a. This operation, as previously described, sets the pump motor 31 into operation, whereby the No. 2 contact of pressure switch closes to complete the circuits through said fuel and air valves 27, 30 and thereby cuts the generator a into full operation.

At sixty seconds in the cycle the No. 2 contact of the cam Ct-1 will open both of the two parallel motor circuits for the motor Ma and, since the No. 1 Contact of the cam Ct-Z is still open there is no closed path for motor current through any of the contacts associated with the timer cam Ct-1 or O42, so the motor Ma will stop, leaving the cam switches 77 and 7S closed and allowing the generator 19a to function to supply its steam to the header 19.

Increasing steam demand Assuming now that the generator 10a is incapable of supplying the demand for steam at the header 19 as reflected by failure ot the No. 1 contact of the pressure switch 8S to open. ln this event, the motor Uf will continue to operate and three minutes after the switch W has been closed (which is two minutes after closure of the No. 1 Contact of the cam control S-l, or one minute after stopping ot the motor Ma), the No. 1 contact of the master timer cam S-2 will close and energize the timer motor MI and set the sub-cycle unit T-Z into operation exactly in the same manner that was described in connection with the sub-cycle unit T-1. Such operation of the sub-cycle unit T-Z will close the contacts 77 and 78 in due course at thirty and forty-tive seconds in the six minute cycle respectively, and if the demand for steam still exists, the control cam S-3 will set its respective sub-cycle unit T-3 into operation five minutes after closure of the switch W or two minutes after the No. 1 contact of the cam S-l has closed.

The operation of the various sub-cycle units T-1 to T-7 inclusive will progress sequentially in the order named as long as there is a progressively increasing demund for steam at the header 19 or until such time as the last sub-cycle unit T-7 has brought its respective generator 10g into operation. Thereafter, i. e. iifteen minutes after the switch W has been closed, the cam S will open switch contact 194 to thus de-energize the circuit ot the motor Uf.

From the above description it will be seen that at sixty seconds in the operation of each sub-cycle unit a period of dwell will exist wherein the respective motors Ma, Mb, Mc, etc., thereof will corne to rest and switches 77 and 78 will remain closed to maintain their associated generator in operation. The generator will continue to function in a normal manner until such time as the demand for steam in the header 19 warrants shutting down that particular generator.

Constant steam demand within a fixed range Assuming now for instance that sub-cycle units T-l, T-Z and T-3 are at their period of dwell with their associated switches 77, 78 closed, that the steam generators 16a, 10b, and 10c are operating and that the remaining generators are in a stand-by condition. If the steam pressure in the header 19 rises to 105 pounds, the No. 1 contacts of the switch 88 will open and the previously described circuit for the motor Uf will become open so as to stop the motor Uf and bring all of the control cams S-1 to S-7 inclusive to a standstill. This dwell in the operation of the various control cams will remain etective during the range existing from 104 pounds to 115 pounds, this being the range between the closing pressures of the Nos. l and 2 contacts of the switch 88. Within this range of pressure the steam generators 10a, 10b and 10c will function normally until such time as thc pressure range isexccc'ded as evidenced by closing of the No. 2 contacts of the switch' 88.

Decreasing steam demand When the pressure of steam in the header rises, during normal daytime operation, to its upper limit, for example pounds7 it reflects a decreased steam demand and closes No. 2 contacts oi the switch 38 to establish a circuit through motor Ur, the circuit exten-ding through switch W, closed contact 9) of switchy V, lead 100, closed No. 2 contacts of switch 8S, lead 122, closed contact 168 of cam switch Si', lead 123,r motor Ur and lead 106. Energization of motor Ur will rotate shaft 107v in a direction to reverse the rotation of all cams of the master timer S and drive them countercloclwise to the positions indicated in Fig. 4. As soon as the previously opened No. 2 contact of the cam S3 is reclosed, a circuit will exist through the sub-cycle timing motor Mc which will permit this sub-cycle timing mechanism to complete or run out its previously interrupted six minute cycle. This circuit exists through lead 110, motor Mc, No. 1 contact of the cani Cl-l (previously closed at the beginning of the sub-cycle dwell), lead 124, and No. 2 contact 0l' cam switch S-B. The motor Mc will thus drive its cams Ct-1, Cif-2, Ct-3 and Ct-4 in a clockwise direction and at one minute and tifteen seconds in the interrupted cycle, i. e. fifteen seconds after the completion of the tirst one minute period of the cycle, the No. 2 contact of the cam Ct-2 will open and the No. 1 contact thereof will close. Opening of the No. 2 contact of the switch (2t-2 will open the motor circuit through this contact but closure of the No. 1 contact of the cam Ct-Z will establish a new motor circuit extending through lead 11i), motor Mc, No. 1 contacts of the cam Ct-l, lead 125, contact No. 1 of the cam Ct-2, and lead 121. The motor Mc will thus continue to drive the cams Ct1, Ct-2, C-S and Ct-4 and during this time the switch 78 of cam Ct-4 will maintain the energizing circuit No. 9 closed through feed pump motor 31.

At one minute and thirty seconds in the cycle, the switch 77 of the cam Ct-3 will open and de-energize the solenoid of the fuel and air valves 27, 30 and thereby close these valves. The switch 78 of the cam Ct-4 however will remain closed until tive minutes and 45 seconds in the sub-cycle, thus allowing ve minutes for the motor 31 to function after the resumption of the interrupted cycle or four minutes and 15 seconds after the fuel and air valves have closed as a result of the opening of their energizing circuits. The prolonged operation of the motor 31 and fuel pump 12 and blower 32 performs the function of cooling down the generator and filling the coil 15 in readiness for renewed operation of the generator should the conditions require `such operation.

At the end of the six minute cycle, Vthe cam Ct-l will cause the No. 1 contacts of the cam Ct-l to open, thus opening the circuit through the motor Ma at which time the cams Ct-l, Ct-2, Ct-S and Cif-4 will assume their original positions as shown in Fig. 4 and the generator 10c will be in a stand-by condition of inactiveness. The master timer cam S-3 however at this time will be in mid-dwell condition wherein the No. 2 contact thereof is closed. it will continue to rotate in a counter-clockwise direction until it assumes its initial position as shown in Fig. 4, at which time the cam Sr, operating as a limit cam, opens its contact 108 after all of the generators have been automatically cut out of operation.

lt will be understood that if, after the No. 2 contact of the master timer cam S-3 is closed during the reverse movement of the cam, Vthe steam pressure in the header 19 is such as to warrant cutting out of the generator 10b, the No. 1 contacts of the pressure switch 88 will remain closed to maintain the circuit previously described through the motor Ur. Two minutes after the No. 2 contact of lthe cam S-3 has closed, the No. 2 contact of the cam S2 will close to allow the interrupted cycle of 13 the sub-cycle unit T-3 to fmishits cycle and reduce the generator 10b to a stand-by condition.

Disabled or malfunctioning generator If one or more of the steam generators 10a to 10g have been purposely disabled, due to manipulation of the respective master switch A in the control mechanism of Fig. 3, or if lany of these generators are disabled due to malfunctioning thereof, the system will operate as intended and in the manner previously described and the sub-cycle unit will enter upon its cycle, become interrupted at the sixty second point in the cycle, and continue the interrupted cycle when directed to' do so by closure of the No. 2 contact of its respective master timer cam S-1, S2, S-3, etc. However, due to the failure of the generator to deliver steam to the header 19 at the designated time, the demand for steam will fall upon the next succeeding generator in the series and although the switches 77 and 78 will close or open 'as the case may be, at their designated time, such opening and closing thereof will either fail to operate the relay mechanism of Fig. 3 which will not be conditioned for such operation or failure of the photoelectric cell I to' actuate the switch H will negative the operation of the relay mechanism.

Aditi-cycle change in steam demand Under certain circumstances an occasion may arise wherein a particular sub-cycle unit has commenced its operation and immediately thereafter a change in the demand for steam will set the reverse drive motor Ur into operation. Under these circumstances the sub-cycle unit will function until the sixty second point of the cycle has been reached and it will not go into the usual dwell but will continue to function to the er1-dof the cycle with- -out interruption. This is made possible by .the provision of the timer cam Ct-2. As previously stated in connection with the sub-cycle mechanism T-1, the sub-cycle uni-t will not commence its operation until the No. 1 contact of the control cam S-1 has closed the circuit extending through lead 110, motor Ma, No. 2 contact of the cam Ct-1, lead 111, and No. 1 contact of the master timer cam S-1. If now this latter contact is opened almost immediately after its initial closure, the motor circuit just described will be broken. But meanwhile the control cam Ct-Z will have established a parallel circuit through the motor Ma extending through lead,110, motor Ma, No, 2 contact of the cam S-Z, lead 120, No. 2 contact of the cam Ct-2 and lead 121.

Low range operation The operation of the timer control mechanism of Fig. 4 is not altered if the switch V is set for a lower range of pressures by closing of the contact 89 thereof and opening of the contact 90. In such case, the switch 87 will prevail over the switch 88 and potential circuits through the motors Uf and Ur will be available for such low pressure regulation of the timer apparatus.

In the case of low pressure operation, .the circuit for the motor Uf exists through the switch W, contact 89 of the switch V, No. 1 contacts of the switch 87, the contacts 199 of a space thermostat 200 which may be arranged in series in the motor circuit, leads 201, 103, contacts 104 of the cam Sf, lead 10r, mot-or Uf and lead 106. The circuit for the motor Ur in the case of low pressure operation extends through the switch W, contact 89 of the switch V, No. 2 contacts of the switch 87 (now closed), leads 202 and 122, contacts 108, lead 123, motor Ur and lead 106. Utilizing these two motor circuits in place of the circuits previously traced through the Nos. 1 and 2 contacts of the switch 88, the operation of the entire control system remains unchanged.

We claim:

l. In combination with a multiple boiler steam generating plant including a steam header for receiving the steam output from each activated boiler of the system,

,electrically activated means individually as'sociatedwith each boiler for delivering fuel, air and water thereto, and electrical control circuits therefor comprising a plurality of cooperative circuit closers including a pair of timer controlled switches operable to energize the control circuits for said electrically activated means, and timer control means responsive to predetermined pressure conditions in said steam header for closing the pairs of timer controlled switches to activate the several boilers in predetermined sequence. v

2.11m combinati-on with a multiple steam generating plant including a steam header for receiving the steam output for each activated boiler of the system, electrically activated means individually associated with each boiler for delivering fuel, air and water thereto, and electrical control circuits therefor comprising a plurality of coopera- `tive circuit closers including a pair of timer controlled switches oper-able to energize said electrically activated means; and timer control means responsive to predetermined vpressure conditions in said steam header for closing the pairs of said timer controlled switches to activate the several boilers in predetermined sequence; the said control circuits for the individual boilers including means directly responsive to the continuance of fire in the individual boilers for maintaining its control circuits elective.

3. In a control system for regulating the operation of a bank of steam generator units arranged in parallel in a steam-generating circuit, each unit including a steam generator provided with a fluid fuel burner and adapted to feed steam into a common steam header, a fuel pump for supplying fuel to said burner, a water pump for sup- -plying feed water to said generator, an electric motor for driving said fuel and water pumps in unison, a normally closed fuel valve interposed between said fuel pump and said burner, a solenoid for opening said fuel valve, an individual control system for each generator unit cornprising an electrical energizing circuit including a relay sw-itch for energizing said motor, a plurality of selectively energized circuits including `an additional relay switch and a plurality of selectively operable switches connected in series therewith for energ-izing said valve opening solenoid, a relay including an actuating magnet for clos-ing both of said relay switches, a circuit for energizing said relay actuating magnet comprising a plurality of cooperating circuit closers including a timer controlled switch, and timer control means responsive to a predetermined pressure in said header for closing said timer controlled switch.

4. In a control system for regulating the operation of a bank of steam generator units arranged in parallel in a steam-generating circuit, each unit including a steam generator provided with a fluid fuel burner and adapted to fe ed steam into a common steam header, a fuel pump for supplying fuel to said burner, a water pump for supplying feed water to said generator, an electric motor for driving s'aid fuel and water pumps in unison, a normally closed fuel valve interposed between said fuel pump and said burner, a solenoid for opening said fuel valve, an individual control system for each generator unit comprising an electrical energizing circuit including a relay switch for energizing said motor, a plurality of selectively energized circuits including an additional relay switch and a plurality of selectively operable switches connected in series therewith for energizing said valve opening solenoid, a relay including an actuating magnet for closing both said relay switches, a circuit for energizing said relay actuating magnet comprising a plurality of cooperative circuit closers including a timer controlled switch, and timer mechanism responsive upon the attain: ment and maintenance of a pressure within a predetermined range in said header for closing said timer controlled switch.

5. In a control system for regulating the operation of a bank of steam-generator units arranged in parallel in a 15 steam-.generating circuit, eachunit including azgenerator provided-with -a liquidfuel burner and kadaptedJtoAfeed steam into a common steam header, afuel pumpvforA supplying liquid fuel to said burner, a waterpump for supplying feed water-to said generator, an electrical motor for driving said fuelrand water pumps in unison, a normally closed fuel valve-interposed between said fuel pump and said burner, a solenoid for opening said fuel valve, an individual control system for. each generator unit comprising an electrical energizing circuit including a relay switch for energizing said motor,.a plurality of selectively energized circuits .including anadditional relay switch and aplurality of selectively operablelswitches .including a timer controlled switch connected in series therewith for energizing said fuel valve opening solenoid, a relay including,anactivatingmagnet for closing both of said relay switches,.a circuit .comprising a plurality of circuit closers including a master relay switch and a relay magnet for closing the same and an additional timer controlled switch connected in series with said master relay switchrand operative in timed relation to thefrst mentioned timer coutrol switch for energizing-the actuating magnet of the lirst mentioned relay subsequent to the closingrof the rst mentioned timer controlled switch, and timerrmechanism responsive to the attainment and maintenance-of a pressure in said header within a predetermined range for actuating the rst` mentioned timer controlled switchY and for-operating said additional timer controlled switch.

6. A combination structure as dened in claim 5 characterized in that said timer mechanism for actuating said timer controlled switches for the individual control system for each of the `several generator units includes separate cam elements operatively engaging said timer lcontrolled switches and further characterized by the provision of separate unidirectional motors for 'each control System of the several generator units to operate both Said cam elements associated with such control system.

7. A combination structure as defined in claim 6 characterized-n-that the timer control mechanismtfor controlling the timer controlled switches for -the individual control systems of the several generator units comprises a cyclicly operable 'subcycle unit^operable upon initial actuation thereof to close said timer controlled switches and to vthereafter become interrupted within the limits of its cycle,

and further-.characterized by the provision of reversible means responsive to the attainment and maintenance of a predeterminedy pressure range in said'header for initially actuating said sub-cycle units in a predetermined sequential order and responsive to the attainment ofapressure higher than said range for initiating completion of the interrupted cycles of said sub-cycle units successively in reverse order.

8. A combination structure as defined in claim 6 charactcrized in that said reversible means is a timer controlled portion of said timer mechanism and functions to control initial energization of vsaid unidirectional motors in a sequential order and is responsive to the attainment of a pressure higher than said predetermined range for energizing saidtuni'directional motors in the reverse order to move said cam elements through the remainder of the interrupted cycle.

'9. The combination structure as defined in claim 8 characterized in that one of 4the selective'ly operable switches in'the 'circuit'for energzing'the'fuel valve opening solenoid is responsive to the water pressure in the'generator.

References' Cited in the file of this patent UNITED STATES PATENTS 1,544,310 Gibson July 30, .1925 1,743,621 Quinn Jan. 1'4, 1930 2,073,072 -Pontow et al Mar. 9, 1937 2,080,924 Logan et al May 18, 1937 2,201,621 LaMont May 21, 1940 2,362,045 Bliss Nov. 7, 1944 A2,403,230 Nagel et al. July-2, 1946 2,470,996 McGrath May 2'4, 1949 

